The production of a highly integrated semiconductor element generally has a series of processes as follows: a conductive thin film such as a metal film as a conductive wiring material and an interlayer dielectric film for insulation between conductive thin films are formed on an element such as a silicon wafer; after that, a photoresist is uniformly applied to the surface thereof to provide a photosensitive layer, and this is subjected to the selective exposure/development treatment to form a desired resist pattern; then the dry etching treatment is applied to the interlayer dielectric film using the resist pattern as a mask to form a desired pattern on the thin film; and then the resist pattern, residue generated by the dry etching treatment (hereinafter referred to as “dry etching residue”), etc. are completely removed by ashing with oxygen plasma, and then cleaning with a cleaning solution or the like.
Recently, the miniaturization of design rules has been accelerated, and the limit of high-speed arithmetic processing has been gradually controlled by signal transmission delay. For this reason, the conductive wiring material has been changed from aluminium to copper which has lower electrical resistance, and the interlayer dielectric film has been changed from a silicone oxide film to a low dielectric constant film (a film having a dielectric constant of less than 3, hereinafter referred to as “low-k film”). However, with the miniaturization of wiring, electromigration of copper easily occurs due to increase in the density of current flowing through the wiring. In response to this, a technique of using cobalt as a highly-reliable wiring material instead of copper and a technique of introducing a cobalt alloy as a cap metal for preventing electromigration of copper have been reported. Further, patterns of 0.2 μm or less have problems in which, for example, the aspect ratio of a pattern of a resist having a film thickness of 1 μm (the ratio obtained by dividing the film thickness of the resist by the line width of the resist) is too large, resulting in collapse of the pattern. In order to solve this, sometimes used is the hard mask method in which: a film containing titanium or silicon (hereinafter referred to as “the hard mask”) is inserted between a pattern film on which a pattern is desired to be actually formed and a resist film; a resist pattern is transferred to the hard mask by dry etching; and after that, this hard mask is used as an etching mask to transfer the pattern to the film on which the pattern is desired to be actually formed by dry etching. In this method, a gas to be used for etching the film on which the pattern is desired to be actually formed may be changed from a gas to be used for etching the hard mask. It is possible to select a gas which can secure a selection ratio with the resist when etching the hard mask and to select a gas which can secure a selection ratio with the hard mask when etching the actual film. For this reason, there is an advantage that a pattern can be formed with a thin resist. Further, a tungsten-containing material is used for a contact plug for connection to a substrate.
When a dry etching residue is removed with oxygen plasma, there is a problem that a low-k film, cobalt and a cobalt alloy, a barrier metal and a barrier insulating film are damaged due to exposure to oxygen plasma or the like, resulting in significant deterioration of electrical characteristics. For this reason, in the production of a semiconductor element using a low-k film, it is desired to employ a method of suppressing damage to a low-k film, cobalt and a cobalt alloy, a barrier metal and a barrier insulating film while removing a dry etching residue at a level comparable to that of an oxygen plasma process. Moreover, for use also for a layer on which a contact plug is exposed, it is sometimes required to suppress damage to a tungsten-containing material. Furthermore, when using a hard mask, it is also required to suppress damage to a material including the hard mask.
Patent Document 1 proposes a method for preventing corrosion of cobalt using benzotriazole, etc. However, when using this method, damage to cobalt cannot be suppressed at a satisfactory level (see Comparative Examples 6 and 9).
Patent Document 2 proposes a method for preventing corrosion of cobalt using a combination of 5-amino-1H-tetrazole and 1-hydroxybenzotriazole. However, when using this method, damage to cobalt cannot be suppressed at a satisfactory level (see Comparative Examples 7 and 10).
Patent Document 3 proposes a method for preventing corrosion of cobalt by forming a corrosion prevention film on cobalt using copper (II) ion, benzotriazole, etc. However, when using this method, damage to cobalt cannot be suppressed at a satisfactory level (see Comparative Examples 8 and 11).
Patent Document 4 proposes a method for preventing corrosion of tungsten using 4-amino-1,2,4-triazole and polyethyleneimine. However, when using this method, damage to a tungsten-containing material cannot be suppressed at a satisfactory level (see Comparative Examples 6, 7 and 8).
Patent Document 5 proposes a method for preventing corrosion of tungsten using a quaternary ammonium salt, pyridinium, bipyridinium and an imidazolium salt. However, when using this method, damage to a tungsten-containing material cannot be suppressed at a satisfactory level (see Comparative Examples 9, 10 and 11).
Patent Document 6 proposes a wiring forming method using a cleaning solution containing phosphoric acid, hydrochloric acid, primary to quaternary amines, an amino acid type surfactant and water. However, when using this cleaning solution, residue cannot be removed at a satisfactory level, and damage to cobalt cannot be suppressed at a satisfactory level. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 12).
Patent Document 7 proposes a wiring forming method using a cleaning solution containing an oxidant, quaternary ammonium hydroxide, alkanolamine, alkali metal hydroxide and water. However, when using this cleaning solution, damage to a tungsten-containing material cannot be suppressed at a satisfactory level. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 13).
Patent Document 8 proposes a wiring forming method using a cleaning solution containing an oxidant, amine, quaternary ammonium hydroxide, alkali metal hydroxide, an organic solvent, a surfactant and water. However, when using this cleaning solution, damage to tungsten cannot be suppressed at a satisfactory level. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 14).
Patent Document 9 proposes a wiring forming method using a cleaning solution containing a fluorine compound, a metal corrosion inhibitor, a passivator and water. However, when using this cleaning solution, residue cannot be sufficiently removed, and damage to a low-k film cannot be suppressed at a satisfactory level. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 15).